POTASH SALTS AND OTHER SALINES IN THE GREAT BASIN REGION. 45 
and of varying depth and filled with brine. (PI. Ill, fig. 1.) The interior of the 
holes is lined with salt crystals. About the edges, surface tension has drawn the 
brine up and the margin of the hole is crusted with efflorescences of salt. Near the 
il land ' ' edge of the rough salt area many holes are to be seen, some more or less arched 
over by salt crusts and dry mud, and always containing water. Areas of soft red mud 
also occur between the rough crusts and the outer margin. These are often difficult 
and dangerous to cross. The formation of the rough salt crusts may often be seen 
upon these mud areas. The explanation appears to be as follows: The surface mud 
dries, forming cracks, and in shrinking leaves narrow channels, bottomed by soft 
mud, between the cracks. Through these channels the brine solution slowly passes 
up and crystallizes, forming veins of salt. As the mud cakes dry, they curl upward 
on the edges, opening the channels wider and allowing more brine to work upward. 
This crystallizes in part and in part is drawn by surface tension over the surface 
already crystallized, forming thicker crusts. The brine in the soft mud below is 
steadily supplied, and the crusts build up until they practically seal the brine over. 
More or less evaporation must continue beneath the crusts, and as the salt crystals 
form they must crowd the mud and crusts up, forming the characteristic windrows 
of mud and salt on the marginal portions. The slow consolidation of the mud, as well 
as the banking up of the ground water on the periphery against the mud mass, would 
account for the upward movement of the brines. Rain water would dissolve the salt 
from the crusts thus formed , and it would collect in small puddles between the rough- 
ened masses, where it would be evaporated to a brine. Surface tension would draw 
this brine up upon the rough masses of salt and, evaporating there, would thicken and 
build up the irregularities of the salt. The evaporation of a salt solution in a beaker 
and the climbing of the salt up the sides is a familiar laboratory phenomenon. 
The smooth area of salt is built up by fresh accessions of brine coming from the 
action of rain water upon the neighboring rough salt areas. Shallow channels (sloughs) 
meander through the rough salt and collect part of the brine formed by the occasional 
rains, discharging it upon the smooth salt, where it is speedily evaporated. Wind- 
blown material collects in the thin sheets of brine and mingles with the salt crystals. 
The general admixture of soil impurities in the rough salt is also explained in this 
way. It is evident that the smooth salt area would eventually reach a level that 
would permit little or no drainage to collect, and the salt bed would no longer be 
built up. Slow consolidation of the silts and clays in the lowest depressions would 
extend the differentiation of level over a long period. Differential consolidation 
would be expected in an area like Death Valley. The finest clays and silts in the 
lowest depression or sink would consolidate at a greater rate than the sand and alluvial 
material forming the greater part of the Death Valley filling. The consolidation of 
the clays and muds would be expected to force the solution upward and even outward. 
The brines forced outward would be diluted by mingling with the underground 
waters coming from the neighboring watersheds. We would expect the marginal 
water to be lower in saline content than that in the smooth salt area, and samples and 
analyses show this to be the case. Reference is made to the results of samples Nos. 
339, 341, and 342. The sample No. 339 was taken on the west side of the valley, due 
west of Furnace Creek Ranch; No. 341 was taken one-fourth mile east of No. 339, and 
No. 342 one-quarter mile east of No. 341. They show, respectively, 2.77, 15.12, and 
34.18 grams total solids per 100 cubic centimeters. 
Campbell states that Death Valley is one of the best watered areas within the Amar- 
gosa region and that the water is, for the most part, good. An inspection of the topo- 
graphic sheet shows many of the water holes to be close to the edge of the central 
playa. At Bennett's wells the water is within 1£ feet of the surface. Most of the 
wells are shallow. The explanation of this has been given under the structural 
development of a playa. 
CHEMICAL DATA FOR DEATH VALLEY. 
Four sets of analyses are given in Tables XXI, XXII, XXIII, and XXIV (Appen- 
dix). The composition of the brines in Table XXI gives perhaps the best conception 
of the character of the salines present in Death Valley. The average percentage of 
ions based upon the percentage of total solids in the order of their magnitude is Na, 
36.12; K, 2.63;'Mg. 0.3; Ca, 0.2; CI, 53.7; S0 4 , 5.62; C0 3 , 0.18. Sodium and chlorine 
are the dominating ions. Carbonates are insignificant in amount. The sulphates are 
in greater amount than in the Silver Peak brines. Potassium is in smaller amount than 
the Silver Peak brines. The sodium-potassium ratio is 13.7; in the Silver Peak brines 
it is 11.9. These ratios indicate parallel conditions in both places. Calcium and mag- 
nesium are insignificant in amount. It should be noted that there is comparative 
agreement between the results obtained upon samples taken by different persons. 
